This invention relates to the field of ultrasound image processing. In particular, the invention relates to ultrasound image processing for inhomogeneous tissue.
The background and description use the context of breast tissue diagnosis. However, the described method and system may also be applied to other forms of tissue, in particular inhomogeneous types of tissue.
Usually, detection and diagnosis of breast cancer is done using x-ray mammography. There are three main problems with this test: it exposes the patient to ionizing radiation; it is less effective in women with dense breast (usually young women); and it cannot be used during an operation, such as biopsy or surgery. On the other hand, B-scan breast ultrasound is harmless, effective in dense breasts, and can easily be used during operations. However, micro-calcifications, which are found to be a significant indicator for breast cancer, are rarely visible in ultrasound images. Moreover, the interpretation of ultrasound images, and especially in the context of identifying micro-calcifications, is strongly dependent on the inspecting doctor.
By mapping the acoustic attenuation from a breast ultrasound image, one can gain a more quantitative marker, which can help in finding breast masses and micro-calcifications, with less dependency on the inspecting doctor. The same approach can be used in characterization of the breast tumours (in particular differentiation between cancerous and benign cases).
Attenuation in ultrasound is the reduction in amplitude of the ultrasound beam as a function of distance through the imaging medium. Accounting for attenuation effects in ultrasound is important because a reduced signal amplitude can affect the quality of the image produced. By knowing the attenuation that an ultrasound beam experiences traveling through a medium, one can adjust the input signal amplitude to compensate for any loss of energy at the desired imaging depth.